Treatment as Prevention Investment The Working Group plans to begin tracking investment in treatment as prevention starting in 2010 for investments in 2009.
What is “Treatment as Prevention”? Treatment as prevention is a broad term sometimes used to describe the use of approved antiretrovirals (ARVs) to lower viral load in people with HIV on the suggestive principle that that they may be less infectious and less likely to transmit HIV to others. (Should other methods of lowering viral load through immunomodulation for example become available they may accomplish the same result.)
Under treatment guidelines operating in many parts of the world for the benefit of the infected patient’s individual health, people with HIV are not urged to start ARVs, by one measure, until their CD4 cell counts have dropped to a specific threshold such as 200, 250 or, perhaps more the consensus now, 350 CD4 cells. Other measures are also significant for individuals in deciding when to commence treatment such as their illness status, presence of co-infections, pregnancy in women or when their viral load exceeds a certain level.
Treatment-as-prevention advocates urge treating people earlier, regardless of CD4 cell count, to optimize the potential prevention impact. New evidence supporting this treat-early approach shows clinical benefits of ARV treatment for the infected individual at as high as a CD4 count of 350. However, no randomized studies have demonstrated the effect of earlier treatment on prevention.
There are data from a growing number of population-wide observation studies, mainly in heterosexual populations, showing a correlation between successfully lowered viral loads and lower risk of transmission to others. Effective and reliably accessed ARV treatment can suppress HIV viral load to low or undetectable levels in an individual’s peripheral blood on a continuing basis. However, even when this indicator of effective treatment is achieved, the virus can be quantitated and measured in semen, in tissue or in other bodily reservoirs. Other data regarding individual partners experience is also encouraging and may yield important information applicable to men who have sex with men.
Several investigators have modeled the potential effect of ARVs on HIV transmission based on the link between high viral load and HIV transmission (Velasco-Hernandez JX, Gershengorn HB, Blower SM. Could widespread use of combination antiretroviral therapy eradicate HIV epidemics? Lancet Infect Dis 2002; 2: 487–93; Montaner JS, Hogg R, Wood E, et al. The case for expanding access to highly active antiretroviral therapy to curb the growth of the HIV epidemic. Lancet 2006; 368: 531–36; Lima VD, Johnston K, Hogg RS, et al. Expanded access to highly active antiretroviral therapy: a potentially powerful strategy to curb the growth of the HIV epidemic. J Infect Dis 2008; 198: 59–67). Using optimistic assumptions, the models have produced encouraging predictions about lowering HIV rates and even eliminating HIV transmission altogether.
If it works, this prevention strategy may protect uninfected sexual partners whose exposure risk to HIV is limited to exposure from these successfully treated patients. A novel and significant expansion of the strategy called “test and treat,” when integrated into coordinated national testing and drug distribution programs, has been proposed to help reduce population wide incidence rates of infection and curtail the epidemic and may be important to accomplish real reductions in HIV acquisition by healthy individuals who can have exposure risk from more than one partner. Either endpoint has been the subject of significant controversy recently and is subject to different supporting rationale.